Metal planes, which are also referred to as metal layers, are electrically interconnected by means of so-called through-plating elements also referred to as via contacts.
In addition to customary via contacts or through-plating elements, so-called high-power through-plating elements are also of importance in integrated circuit technology in order to be able to recognize applications which require a high current-carrying capacity.
Furthermore, high-power through-plating elements provide a low-impedance transition between different metal plates. Low-impedance contact-making is required in particular for electrically connecting a final to a penultimate metal plane or metal layer. Preferably in a process sequence terminal units for connecting external circuit units are formed together with through-plating elements and accommodated in a housing of an integrated circuit device.
An essential problem in the fabrication of through-plating elements, high-power through-plating elements and terminal units in a single process sequence is that the through-plating elements, the high-power through-plating elements and the terminal units have structure sizes that differ considerably. However, it is necessary for cost reasons that no additional processes or even additional process levels must be with respect to a process sequence or in a process sequence. In particular the abovementioned problem arises in the context of increasing miniaturization in future technology generations.
Conventional fabrication technologies produce through-plating elements, high-power through-plating elements and terminal units by means of hot aluminum sputtering (aluminum reflow). In the context of a required decrease in size (miniaturization requirement) of the through-plating elements, this process, in a disadvantageous manner, no longer operates viably for future technology generations.
FIG. 2 shows two process steps of a conventional method for fabricating through-plating elements (a), high-power through-plating elements (b) and terminal units (c).
Process step (A) shows how an insulation layer 102 is applied on a substrate 101, the structures of the applied insulation layer 102 having different lateral dimensions. In the case of a conventional filling of the depressions between the structures of the insulation layer 102 and onto the insulation layer 102 by means of a terminal or connecting layer 104 the problem arises that, in the case of small structure sizes and in particular in the case of relatively large structure depths, an unreliable filling of through-plating arrangements arises as indicated by the arrows (I) in FIG. 2.
Consequently, this type of hot aluminum sputtering is suitable for high-power through-plating elements and terminal units of a relatively large lateral dimension in the structure size while the through-plating elements of a smaller structure size that are always present cannot be reliably formed. Furthermore, a disadvantage of the conventional methods for fabricating integrated circuit units is that the hot aluminum sputtering impedes a subsequent lithography step owing to the resultant high degree of roughness of the metal surface in the course of alignment. This is becoming more and more critical, particularly in future technology generations.
In order to solve this problem, it has been proposed to provide the through-plating elements by filling the depressions of the patterned insulation layer 102 with tungsten as shown in FIG. 3, process step (B). The contact-making layer 103 formed from tungsten material then fills all the structures and the corresponding depressions.
Process step (C) shown in FIG. 3 then provides for the contact-making layer 103 to be polished back to a structure size of the insulating layer 102. While the polishing-back process, also referred to as chemical mechanical polishing (CMP), can be carried out satisfactorily in the case of the through-plating elements of a small structure size, as shown in FIG. 3(a), considerable problems arise in the case of the high-power through-plating elements (FIG. 3(b)) and the terminal units (FIG. 3(c)). The disadvantages in the case of the high-power through-plating elements and terminal units consist in the fact that tungsten inexpediently represents a high contact resistance, as shown by an arrow (II) in FIG. 3(b) and an arrow (III) in FIG. 3(c), with the result that the desired current-carrying capacity of the high-power through-plating elements is reduced.
It is furthermore disadvantageous that the terminal units exhibit a so-called “dishing” effect, as shown by an arrow (IV) in FIG. 3(c), i.e. dish-shaped depressions form during the CMP process, the dish-shaped depression, in a disadvantageous manner, not being reproducible, moreover. This results in the disadvantage that the CMP process produces particles that adversely affect the fabrication process of the integrated circuit device. Furthermore, a later bonding by the contact-making layer 104 formed from tungsten material is disturbed (arrow (III) in FIG. 3(c)).
Process step (D) shown in FIG. 3 includes a coating of the structures with which contact is made by tungsten by means of a connecting layer 104 formed, for example, from aluminum. This connecting layer, in a disadvantageous manner, likewise has a “dishing” effect in the case of the high-power through-plating elements and the terminal units, as shown by the arrow (IV) in FIG. 3(c).
In order to solve this problem that occurs as a result of the processing of different structure sizes it has been proposed to provide small structure sizes which are used uniformly for through-plating elements, high-power through-plating elements and terminal units as shown in FIG. 4.
The disadvantage that arises in this case, however, is that the high-power through-plating elements have an impaired current-carrying capacity since a contact-making layer 103 formed from tungsten is used for making contact in the lateral structures (now reduced in size) of the insulation layer 102, as shown by means of an arrow (V) in FIG. 4(b). FIG. 4(c) shows that disadvantages also arise with the terminal units which by means of small structure sizes which correspond to those of the through-plating elements (FIG. 4(a)). These disadvantages consist in the fact that tungsten is once again used for making contact, and impedes a necessary bonding of terminal devices such as wires, for example, to the terminal units of the integrated circuit device, as shown by an arrow (VI) in FIG. 4(c).
Therefore, with the conventional methods shown with reference to FIGS. 2, 3 and 4, it is not possible to achieve a cost-effective and reliable provision of through-plating elements, high-power through-plating elements and terminal units in a uniform process sequence.